Distribution of chondroitin sulphate proteoglycans and peanut agglutinin-binding molecules during bovine fetal palatine ridge formation.

The expression of proteoglycans detected by the monoclonal antibodies MO-225, 3B3 and 2B6 and of peanut agglutinin-binding molecules was examined histochemically during the development of bovine palatine ridge (PR) rudiments in fetuses with crown-rump lengths of 4-60 cm. The bovine PR rudiment has 2 characteristic developmental stages: the 1st is the positioning of the epithelial placode (EP) to the predetermined site of PR rudiment formation and the 2nd is the reorientation of the apical edge of PR rudiments to form wave-like patterns from mouth to pharynx. During the 1st stage, chondroitin 6-sulphate (C6S) was expressed strongly at the epithelial basement membrane just beneath the EP. During the 2nd stage, both C6S and disaccharide unit of Glc2sulphate-GalNAc6sulphate (GlcAsSO4-GalNAc6SO4) were distributed at the basement membrane and the mesenchyme just beneath the steeper wall of the PR rudiment. Peanut agglutinin-binding molecules were also detected in the mesenchyme, their distribution being similar to that for C6S and GlcA2SO4-GalNAc6SO4, and additionally in the epithelial cells after formation of the wave-like PR. The distribution of dermatan sulphate was not directly related to the developmental changes of PR rudiments, but it was detected in the lower mesenchymal layer which supported the protruding site of the PR rudiment after the 2nd stage. The results suggest that 2 different types of proteoglycan may be involved in the critical periods during the morphogenesis of the bovine PR rudiments.